Dynamoelectric machines come in widely varying shapes, sizes and capacities. Some are employed as motors while others are employed as generators. And some are employed as combination motors-generators, meaning that they can be operated either as a motor or as a generator, depending upon exactly what function is desired of the machine at a given point in time.
In some cases, volume and weight constraints are minimal, while in others they are critical. For example, in aerospace applications, weight is always a concern. Volume constraints are also a concern lest the machine occupy too much space on an aircraft or even contribute to a less efficient aerodynamic shape as a result of its bulk.
Most such machines have a shafted rotor which is to say that a single shaft extends through the rotor body to journal the same for rotation about an axis within a stator. This is, however, not always desirable. For example, in some machines, the presence of a shaft extending through the rotor body may interfere with the magnetic flux path of the machine and thus contribute to magnetic inefficiency which in turn may lower the capacity of a machine having a given size. This is particularly true in dynamoelectric machines having a relatively small number of poles on the rotor. In such cases, it may be desirable to provide a shaftless rotor. See, for example, commonly assigned U.S. Pat. No. 4,562,641 issued Jan. 7, 1986 to Mosher et al. In other cases, the presence of a single shaft may contribute to weight and/or dictate enlargement of the rotor for a given application in that rotor components cannot be located in the area of the rotor occupied by the shaft. This in turn requires that such components be located elsewhere in the rotor which may increase its size in order to house the components and/or may decrease magnetic efficiency as a result of locating such components radially outward of the shaft. In such cases it would be desirable to provide a shaftless rotor for the purpose of reducing weight and/or allowing the part of the rotor that would otherwise be occupied by the shaft to be used for housing other rotor components to thereby reduce overall rotor size. It would also be desirable from the standpoint of reducing the mass of the rotating components of the dynamoelectric machine to enhance the ability of the dynamoelectric machine to operate at high speed.
The present invention is directed to providing such a shaftless rotor for a dynamoelectric machine.